Recent research in myocardial tissue engineering has demonstrated the promise of mechanically robust microfabricated biomaterials that combine elasticity and strength, and cell-based strategies that enhance the survival and vascular integration of transplanted heart and/or stem cells. However, creation of myocardial grafts capable of organized contractile function, and a means to rapidly vascularize thick myocardial grafts upon implantation remain unsolved problems that currently limit the dimensions and clinical translation of new myocardial regenerative technologies. Scalable units for building vascularized cardiac grafts comprised of heart cells, endothelial cells, and slowly biodegradable elastomeric scaffolds would be a paradigm shift in the regeneration of myocardium rendered non-functional by ischemia or congenital heart disease. The goals of the proposed work are to: (i) design elastomeric scaffolds that provide parenchymal spaces for culturing and aligning heart cells, (ii) combine these building blocks with perfusable channel networks that provide intravascular spaces for culturing endothelial cells, and (iii) show that the resulting myocardial grafts can provide mechanical support and viable, transplanted heart cells after myocardial infarction (MI) in a rodent model. In Aim 1, we will create elastomeric scaffolds from poly (glycerol-sebacate) and elastin, and test the hypothesis that scaffold structural features (i.e., rectangular pores combined with aligned elastin microfibers) will guide the elongation, alignment, and contractility of cultured heart cells. In Aim 2, we will combine building blocks (i.e., elastomeric scaffolds with cultured heart cells) and perfusable channel networks to form scalable units comprised of intravascular and parenchymal spaces. We will test the hypotheses that perfusion of the intravascular spaces will enhance heart cell survival in the parenchymal spaces, and we will line the channels with endothelial cells in vitro. In Aim 3, we will evaluate the myocardial grafts in rodents after surgically induced MI by using four experimental groups: (i) elastomeric scaffolds with intravascular endothelial cells and parenchymal heart cells; (ii) elastomeric scaffolds with only heart cells, (iii) elastomeric scaffolds without any cells, and (iv) untreated MI. We will test the hypotheses that elastomeric scaffolds will preserve ventricular function post-MI, exogenous heart cells will survive and integrate electromechanically with host myocardium, and endothelialized channels will form functional anastomoses with host vessels. The main novelties of this work are the design and demonstration of: (i) elastomeric building-block scaffolds for tissue engineering and regenerative medicine, (ii) lamellar scalable units comprised of intravascular and parenchymal compartments for regenerating highly vascularized tissues (e.g., cardiac, skeletal and smooth muscle, liver, kidney), and (iii) anisotropic scaffolds for regenerating other anisotropic, load-bearing tissues (e.g., blood vessel, ligament, tendon, cartilage, and bone).